Apparatus for manufacturing ultrathin substrate using a laminate body

ABSTRACT

Provided is a laminated body comprising a substrate to be ground and a support, where the substrate is ground to a very small thickness and can then be separated from the support without damaging the substrate. One embodiment of the present invention is a laminated body comprising a substrate to be ground, a joining layer in contact with the substrate to be ground, a photothermal conversion layer comprising a light absorbing agent and a heat decomposable resin, and a light transmitting support. After grinding the substrate surface which is opposite that in contact with the joining layer, the laminated body is irradiated through the light transmitting layer and the photothermal conversion layer decomposes to separate the substrate and the light transmitting support.

RELATED APPLICATIONS

This is a divisional application which claims priority to now issuedU.S. Pat. No. 7,988,807, filed Jan. 28, 2009, which in turn claimspriority to now issued U.S. Pat. No. 7,534,498, filed Jun. 2, 2003, bothof which claim priority to Japanese Pat. Apps. 2002-161,846, filed Jun.3, 2002 and 2002-350,247, filed Dec. 2, 2002, the disclosures of whichare herein incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a laminated body where a substrate tobe ground, such as silicon wafer, fixed on a support can be easilyseparated from the support, and also relates to a method and anapparatus for manufacturing this laminated body and a method and anapparatus for producing a thinned substrate.

BACKGROUND

In various fields, reducing the thickness of a substrate often isdesired. For example, in the field of quartz devices, reducing thethickness of a quartz wafer is desired so as to increase the oscillationfrequency. Particularly, in the semiconductor industry, efforts tofurther reduce the thickness of a semiconductor wafer are in progress torespond to the goal of reducing the thickness of semiconductor packagesas well as the high-density fabrication by chip lamination technology.Thickness reduction is performed by so-called back side grinding of asemiconductor wafer on the surface opposite that containingpattern-formed circuitry. Usually, in conventional techniques ofgrinding the back side, or surface, of a wafer and conveying it whileholding the wafer with only a backgrinding protective tape, thicknessreduction can be accomplished in practice only to a thickness of about150 micrometers (μm) because of problems such as uneven thickness of theground wafer or warping of the wafer with protective tape aftergrinding. For example, Japanese Unexamined Patent Publication (Kokai)No. 6-302569 discloses a method where a wafer is held on a ring-formframe through a pressure-sensitive adhesive tape, the back surface ofthis wafer held on the frame is ground and the wafer is conveyed to thenext step. However, this method has not yet attained a remarkableimprovement over the present level of wafer thickness which may beobtained without encountering the aforementioned problems of unevennessor warpage.

A method of grinding the back surface of a wafer and conveying it whilefirmly fixing the wafer on a hard support through an adhesive agent hasalso been proposed. This intends to prevent the breakage of a waferduring the back surface grinding and conveyance by supporting the waferusing such a support. According to this method, a wafer can be processedto a lower thickness level as compared with the above-described method,however, the ultrathin wafer cannot be separated from the supportwithout breaking the wafer and therefore, this method cannot bepractically used as a method of thinning a semiconductor wafer.

SUMMARY

Accordingly, the object of the present invention is to provide alaminated body in which a substrate to be ground is fixed on a supportand the substrate to be ground can be easily peeled off from thesupport. The object of the present invention includes providing a methodfor manufacturing the laminated body, and a method and an apparatus formanufacturing an ultrathin substrate using the laminated body.

In one embodiment of the present invention, a laminated body isprovided, the laminated body comprising a substrate to be ground; ajoining layer in contact with said substrate to be ground; aphotothermal conversion layer comprising a light absorbing agent and aheat decomposable resin; and a light transmitting support. Aftergrinding the substrate surface which is opposite that in contact withthe joining layer, the laminated body can be irradiated through thelight transmitting layer to decompose the photothermal conversion layerand to separate the substrate and the light transmitting support. Inthis laminate, the substrate ground to a very small thickness can beseparated from the support without breaking the substrate.

In another embodiment of the present invention, a method formanufacturing the above-described laminated body is provided, the methodcomprising coating on a light transmitting support a photothermalconversion layer precursor containing a light absorbing agent and a heatdecomposable resin solution, or a monomer or oligomer as a precursormaterial of a heat decomposable resin; drying to solidify or cure thephotothermal conversion layer precursor to form a photothermalconversion layer on the light transmitting support; applying an adhesiveto a substrate to be ground or to the photothermal conversion layer toform a joining layer; and joining the substrate to be ground and thephotothermal conversion layer by means of the joining layer underreduced pressure to form a laminated body.

By joining the substrate to be ground and the light transmitting supportthrough the joining layer under reduced pressure, bubbles and dustcontamination is prevented from forming inside the laminated body, sothat a level surface can be formed and the substrate can maintain theevenness of thickness after grinding.

In still another embodiment of the present invention, an apparatus formanufacturing the above-described laminated body is provided, where aphotothermal conversion layer formed on a light transmitting support islaminated on a substrate to be ground through a joining layer underreduced pressure, the apparatus comprising (1) a vacuum chamber capableof being reduced to a predetermined pressure, (2) a supporting partprovided in the vacuum chamber, on which is disposed either (i) asubstrate to be ground or (ii) a light transmitting support havingphotothermal conversion layer formed thereon, and (3) aholding/releasing means provided in the vacuum chamber and movable inthe vertical direction at the upper portion of the supporting part,which can hold the other one of the substrate to be ground or the lighttransmitting support having a photothermal conversion layer formedthereon at its peripheral edges and can also release it when thesubstrate to be ground and the photothermal conversion layer are inclose proximity.

When this apparatus is used, bubbles and dust contamination can beprevented from forming in the laminated body because the laminated bodyis manufactured under reduced pressure, and also the surface to belaminated is not damaged by the holding/releasing means.

In still another embodiment of the present invention, a method formanufacturing a reduced thickness substrate is provided, the methodcomprising preparing the above-described laminated body, grinding thesubstrate to a desired thickness, irradiating the photothermalconversion layer through the light transmitting support to decompose thephotothermal conversion layer and thereby to separate the substrate fromthe light transmitting support after grinding, and peeling the joininglayer from the substrate after grinding. In this method, a substrate canbe ground to a desired thickness (for example, 150 μm or less,preferably 50 μm or less, more preferably 25 μm or less) on a supportand after grinding the support is separated from the substrate usingexposure to radiation energy, so that the joining layer remaining on thesubstrate after grinding can be easily peeled off from the substrate.

In still another embodiment, the invention provides An apparatus formanufacturing a ground substrate, comprising a grinder adapted forgrinding the substrate of the laminated body as described above anddescribed below in greater detail, a radiation energy source capable ofproviding a sufficiently high radiation energy to said photothermalconversion layer through said light transmitting support to decomposesaid photothermal conversion layer and thereby to separate saidsubstrate and said light transmitting support after grinding, and aseparator adapted for removing said joining layer from said substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a)-(f) show cross-sectional views of several embodiments of thelaminated body of the present invention.

FIGS. 2( a) and (b) show cross-sectional views of a vacuum adhesiondevice useful in the present invention.

FIG. 3 is a partial cross-sectional view of a grinding device useful inthe method of the present invention.

FIGS. 4( a), (a′) and (b)-(e) show the steps of separating the supportand peeling the joining layer.

FIG. 5 is a cross-sectional view of a laminated body fixing device whichcan be used in the laser beam irradiation step.

FIGS. 6( a)-(e) are perspective views of laser irradiation devicesuseful in the present invention.

FIG. 6( f) is a drawing showing energy distribution of a top hat form.

FIG. 7( a) is a schematic view of a pick-up used in the operation ofseparating wafer and support, wherein the pick-up is in the center ofthe support.

FIG. 7( b) is a schematic view of a pick-up used in the operation ofseparating wafer and support, wherein the pick-up is at the edge part ofthe support.

FIG. 8 is a schematic view showing how the joining layer is peeled fromthe wafer.

FIG. 9 is a schematic view of an apparatus for measuring the adhesivestrength of the joining layer.

DETAILED DESCRIPTION

One important constituent feature of the laminated body of the presentinvention is that a photothermal conversion layer is provided betweenthe substrate to be ground and the light transmitting support. Thephotothermal conversion layer decomposes upon irradiation with radiationenergy such as laser beam, whereby the substrate can be separated fromthe support without causing any breakage. Therefore, the inventionprovides a substrate thinned to a range of thickness not achievable byconventional methods.

FIG. 1 shows some embodiments of the laminated body of the presentinvention. In the laminated body 1 of FIG. 1( a), a substrate 2 to beground, a joining layer 3, a photothermal conversion layer 4 and asupport 5 are laminated in this order. Also, as shown in FIG. 1( b), thejoining layer 3 may be a double-faced adhesive tape 8 comprising a firstintermediate layer (film) 6 having provided on both surfaces thereof apressure-sensitive adhesive agent 7. Furthermore, as shown in FIGS. 1(c) and (d), the joining layer 3 may be a double-faced adhesive tape 8integrated with the photothermal conversion layer 4. Still further, asshown in FIG. 1( e), the joining layer 3 may be a double-faced adhesivetape 8 in which the photothermal conversion layer 4 itself comprises apressure-sensitive adhesive photothermal conversion layer 4′ having apressure-sensitive adhesive characteristics. As shown in FIG. 1( f), itis also possible that a first intermediate layer 6 is provided betweenthe joining layer 3 and the photothermal conversion layer 4, a secondintermediate layer 9 is provided between the photothermal conversionlayer 4 and the support 5, and the second intermediate layer 9 and thesupport 5 are joined through another joining layer 3′.

The elements comprising the laminated body of the present invention aredescribed in greater detail below.

Substrate

The substrate may be, for example, a brittle material difficult to thinby conventional methods. Examples thereof include semiconductor waferssuch as silicon and gallium arsenide, a rock crystal wafer, sapphire andglass.

Light Transmitting Support

The light transmitting support is a material capable of transmittingradiation energy, such as a laser beam used in the present invention,and the material is required to keep the ground body in a flat state andnot cause it to break during grinding and conveyance. The lighttransmittance of the support is not limited as long as it does notprevent the transmittance of a practical intensity level of radiationenergy into the photothermal conversion layer to enable thedecomposition of the photothermal conversion layer. However, thetransmittance is preferably, for example, 50% or more. Also, in order toprevent the ground body from warping during grinding, the lighttransmitting support preferably has a sufficiently high stiffness andthe flexural rigidity of the support is preferably 2×10⁻³ (Pa·m³) ormore, more preferably 3×10⁻² (Pa·m³) or more. Examples of usefulsupports include glass plates and acrylic plates. Furthermore, in orderto enhance the adhesive strength to an adjacent layer such asphotothermal conversion layer, the support may be surface-treated with asilane coupling agent or the like, if desired. In the case of using aUV-curable photothermal conversion layer or joining layer, the supportpreferably transmits ultraviolet radiation.

The support is sometimes exposed to heat generated in the photothermalconversion layer when the photothermal conversion layer is irradiated orwhen a high temperature is produced due to frictional heating duringgrinding. Also, for the purpose of forming a metal film on the substratea process such as vapor deposition, plating or etching may beadditionally provided before separating the ground substrate from thesupport. Particularly, in the case of a silicon wafer, the support issometimes subjected to a high-temperature process to form an oxide film.Accordingly, a support having heat resistance, chemical resistance and alow expansion coefficient is selected. Examples of support materialshaving these properties include borosilicate glass available as Pyrex™and Tenpax™ and alkaline earth boro-aluminosilicate glass such asCorning™ #1737 and #7059.

To obtain the desired thickness uniformity after grinding of thesubstrate, the thickness of the support is preferably uniform. Forexample, for grinding a silicon wafer to 50 μm or less and attainingevenness of ±10% or less, the variability in the thickness of thesupport must be reduced to ±2 μm or less. In the case where the supportis repeatedly used, the support also preferably has scratch resistance.For repeatedly using the support, the wavelength of the radiation energyand the support must be selected to suppress the damage to the supportby the radiation energy. For example, when Pyrex glass is used as thesupport and a third harmonic generation YAG laser (355 nm) is employed,the separation of the support and the substrate can be performed,however, such a support exhibits low transmittance at the wavelength ofthis laser and absorbs the radiation energy, as a result, the support isthermally damaged and cannot be reused in some cases.

Photothermal Conversion Layer

The photothermal conversion layer contains a light absorbing agent and aheat decomposable resin. Radiation energy applied to the photothermalconversion layer in the form of a laser beam or the like is absorbed bythe light absorbing agent and converted into heat energy. The heatenergy generated abruptly elevates the temperature of the photothermalconversion layer and the temperature reaches the thermal decompositiontemperature of the heat decomposable resin (organic component) in thephotothermal conversion layer resulting in heat decomposition of theresin. The gas generated by the heat decomposition is believed to form avoid layer (such as air space) in the photothermal conversion layer anddivide the photothermal conversion layer into two parts, whereby thesupport and the substrate are separated.

The light absorbing agent absorbs radiation energy at the wavelengthused. The radiation energy is usually a laser beam having a wavelengthof 300 to 11,000 nanometers (nm), preferably 300 to 2,000 nm andspecific examples thereof include a YAG laser which emits light at awavelength of 1,064 nm, a second harmonic generation YAG laser at awavelength of 532 nm, and a semiconductor laser at a wavelength of 780to 1,300 nm. Although the light absorbing agent varies depending on thewavelength of the laser beam, examples of the light absorbing agentwhich can be used include carbon black, graphite powder, microparticlemetal powders such as iron, aluminum, copper, nickel, cobalt, manganese,chromium, zinc and tellurium, metal oxide powders such as black titaniumoxide, and dyes and pigments such as an aromatic diamino-based metalcomplex, an aliphatic diamine-based metal complex, an aromaticdithiol-base metal complex, a mercaptophenol-based metal complex, asquarylium-based compound, a cyanine-based dye, a methine-based dye, anaphthoquinone-based dye and an anthraquinone-based dye. The lightabsorbing agent may be in the form of a film including a vapor depositedmetal film. Among these light absorbing agents, carbon black isparticularly useful, because the carbon black significantly decreasesthe force necessary for separating the substrate from the support afterthe irradiation and accelerates the separation.

The concentration of the light absorbing agent in the photothermalconversion layer varies depending on the kind, particle state(structure) and dispersion degree of the light absorbing agent but theconcentration is usually from 5 to 70 vol % in the case of generalcarbon black having a particle size of approximately from 5 to 500 nm.If the concentration is less than 5 vol %, heat generation of thephotothermal conversion layer may be insufficient for the decompositionof the heat decomposable resin, whereas if it exceeds 70 vol %, thephotothermal conversion layer becomes poor in the film-forming propertyand may readily cause failure of adhesion to other layers. In the casewhere the adhesive used as the joining layer is a UV-curable adhesive,if the amount of carbon black is excessively large, the transmittance ofthe ultraviolet ray for curing the adhesive decreases. Therefore, in thecase of using a UV-curable adhesive as the joining layer, the amount ofcarbon black should be 60 vol % or less. In order to reduce the force atthe time of removing the support after irradiation and thereby preventabrasion of the photothermal conversion layer during grinding (such asabrasion due to abrasive in wash water), carbon black is preferablycontained in the photothermal conversion layer in an amount of 20 to 60vol %, more preferably from 35 to 55 vol %.

Examples of the heat decomposable resin which can be used includegelatin, cellulose, cellulose ester (e.g., cellulose acetate,nitrocellulose), polyphenol, polyvinyl butyral, polyvinyl acetal,polycarbonate, polyurethane, polyester, polyorthoester, polyacetal,polyvinyl alcohol, polyvinylpyrrolidone, a copolymer of vinylidenechloride and acrylonitrile, poly(meth)acrylate, polyvinyl chloride,silicone resin and a block copolymer comprising a polyurethane unit.These resins can be used individually or in combination of two or morethereof. The glass transition temperature (Tg) of the resin ispreferably room temperature (20° C.) or more so as to prevent there-adhesion of the photothermal conversion layer once it is separateddue to the formation of a void layer as a result of the thermaldecomposition of the heat decomposable resin, and the Tg is morepreferably 100° C. or more so as to prevent the re-adhesion. In the casewhere the light transmitting support is glass, in order to increase theadhesive force between the glass and the photothermal conversion layer,a heat decomposable resin having within the molecule a polar group(e.g., —COOH, —OH) capable of hydrogen-bonding to the silanol group onthe glass surface can be used. Furthermore, in applications requiring achemical solution treatment such as chemical etching, in order to impartchemical resistance to the photothermal conversion layer, a heatdecomposable resin having within the molecule a functional group capableof self-crosslinking upon heat treatment, a heat decomposable resincapable of being crosslinked by ultraviolet or visible light, or aprecursor thereof (e.g., a mixture of monomers and/or oligomers) may beused. For forming the photothermal conversion layer as apressure-sensitive adhesive photothermal conversion layer as shown inFIG. 1( e), a pressure-sensitive adhesive polymer formed frompoly(meth)acrylate or the like, as may be used for the heat decomposableresin, is employed.

Transparent Filler

The photothermal conversion layer may contain a transparent filler, ifdesired. The transparent filler acts to prevent the re-adhesion of thephotothermal conversion layer once it is separated due to the formationof a void layer as a result of the thermal decomposition of the heatdecomposable resin. Therefore, the force required for the separation ofthe substrate and the support, after grinding of the substrate andsubsequent irradiation, can be further reduced. Furthermore, since there-adhesion can be prevented, the latitude in the selection of the heatdecomposable resin is broadened. Examples of the transparent fillerinclude silica, talc and barium sulfate. Use of the transparent filleris particularly advantageous when a UV-curable adhesive is used as thejoining layer. This is presently believed to be due to the followingreasons. When a particulate light absorbing agent such as carbon blackis used, the light absorbing agent has a function of reducing the forcefor separation and also functions to disrupt the transmittance ofultraviolet light. Therefore, when a UV-curable adhesive is used as thejoining layer, the curing may not proceed satisfactorily or may requirea very long time. In such a case, when a transparent filler is used, thesubstrate and the support can be separated easily after irradiationwithout disturbing the curing of the UV-curable adhesive. The amount ofthe transparent filler can be determined, when a particulate lightabsorbing agent such as carbon black is used, by the total amount withthe light absorbing agent. The total amount of the particulate lightabsorbing agent (e.g., carbon black) and the transparent filler in thephotothermal conversion layer is preferably from 5 to 70 vol % based onthe volume of the photothermal conversion layer. With the total amountin this range, the force for the separation of the substrate and thesupport can be sufficiently reduced. However, the force for theseparation is also affected by the shape of the particulate lightabsorbing agent and the transparent filler. More specifically, the forcefor the separation is sometimes more effectively reduced with a smallfiller amount in the case where the particle shape is complicated (aparticle state resulting from more complex structure) than in the casewhere the particle shape is relatively simple, such as nearly spherical.

Therefore, the total amount of the particulate light absorbing agent andthe transparent filler is prescribed based on the “top filler volumeconcentration” (TFVC) in some cases. This means a filler volumeconcentration such that when a mixture of the particulate absorbingagent and the transparent filler is left standing in a dry state and theheat decomposable resin is mixed with the filler in an amount of justfilling the volume of voids. That is, the TFVC when the heatdecomposable resin is mixed with the filler in an amount of just fillingthe volume of voids in the mixture of the particulate light absorbingagent and the transparent filler is 100% of the top filler volumeconcentration. The total amount of the particulate light absorbing agentand the transparent filler in the photothermal conversion layer ispreferably 80% or more, more preferably 90% or more, of the top fillervolume concentration. In further explanation, the total volumepercentage of the fillers (e.g., carbon black and transparent filler) isrepresented by “A”, and the Top Filler Volume Concentration, TFVC (totalvolume percentage of the fillers with resin filling the void volume ofthe fillers) is represented by “B”, then A/B preferably is greater thanabout 80%, (more preferably A/B>90%).

The void volume of the fillers can be shown as oil absorption with theliquid amount required to fill the void volume of fillers by the unitweight. Regarding carbon black, the measured number in the vendorcatalogue is used, and regarding transparent filler (e.g., silica), ageneral number (200 g/cc) of this kind of silica is used.

While not being bound by any theory, it is presently believed that thelight absorber (e.g., carbon black) in the photothermal conversion layerabsorbs the laser energy that is irradiated through the transparentsupport and converts it into heat, which decomposes the matrix-resin andgenerates gas or voids. As a result, the voids separate this layer intoparts such as two layers, and then the semiconductor wafer is releasedfrom the support. The surface separated by the voids can re-contact thesurfaces, given time. The surface has carbon black particles as well asresidual resin, which resin is reduced in molecular weight by thermaldecomposition. In re-contacting (e.g., re-adhering), this residual resincan increase adhesion. On the other hand, when not only the photothermalconversion layer but also the adhesive layer is soft, the re-contactingarea can be relatively large, which makes the adhesion larger and makesit very difficult to release the ultra-thinned wafer from the supportwithout damage or breaking. In this invention, by setting A/B>80%,preferably A/B>90%, the residual resin on the release surface isreduced. Thereby the adhesion generated by re-contacting can beminimized. Further, by raising the amount of carbon black together withusing the transparent filler to meet A/B>80%, or 90%, the thicknessdesired for the photothermal conversion layer at least can be kept, andsimultaneously UV transparency such as is desired when the adhesivelayer is of the UV cure type.

Thus, with the total amount in this range, the substrate and the supportare easily separated after irradiation.

The thickness of the photothermal conversion layer is generally around0.5 μm. If the thickness is to low, partial exposure of the adjacentadhesive layer to release surface occurs, which can raise adhesion ofthe release surface especially when the adhesive layer is relativelysoft, and this can result in difficult removable (without breakage) ofthe ultra-thinned wafer.

The photothermal conversion layer may contain other additives, ifdesired. For example, in the case of forming the layer by coating a heatdecomposable resin in the form of a monomer or an oligomer andthereafter polymerizing or curing the resin, the layer may contain aphoto-polymerization initiator. Also, the addition of a coupling agent(integral blend method, i.e., the coupling agent is used as an additivein the formulation rather than as a pre-surface-treatment agent) forincreasing the adhesive force between the glass and the photothermalconversion layer, and the addition of a crosslinking agent for improvingthe chemical resistance are effective for their respective purposes.Furthermore, in order to promote the separation by the decomposition ofthe photothermal conversion layer, a low-temperature gas generator maybe contained. Representative examples of the low-temperature gasgenerator which can be used include a foaming agent and a sublimatingagent. Examples of the foaming agent include sodium hydrogencarbonate,ammonium carbonate, ammonium hydrogencarbonate, zinc carbonate,azodicarbonamide, azobisisobutylonitrile,N,N′-dinitrosopentamethylenetetramine, p-toluenesulfonylhydrazine andp,p-oxybis(benzenesulfonylhydrazide). Examples of the sublimating agentinclude 2-diazo-5,5-dimethylcyclohexane-1,3-dione, camphor, naphthalene,borneol, butyramide, valeramide, 4-tert-butylphenol, furan-2-carboxylicacid, succinic anhydride, 1-adamantanol and 2-adamantanone.

The photothermal conversion layer can be formed by mixing the lightabsorbing agent such as carbon black, the heat decomposable resin and asolvent to prepare a precursor coating solution, coating this solutionon the support, and drying it. Also, the photothermal conversion layercan be formed by mixing the light absorbing agent, a monomer or anoligomer as a precursor material for the heat decomposable resin and,optionally, additives such as photo-polymerization initiator, and asolvent, if desired, to prepare a precursor coating solution in place ofthe heat decomposable resin solution, coating the solution on thesupport, drying and polymerizing/curing it. For the coating, a generalcoating method suitable for coating on a hard support, such as spincoating, die coating, and roll coating, can be used. In the case offorming the photothermal conversion layer in a double-faced tape asshown in FIGS. 1( c) to (e), the photothermal conversion layer can beformed on a film by using a coating method such as die coating, gravurecoating, and knife coating.

In general, the thickness of the photothermal conversion layer is notlimited as long as it permits the separation of the support and thesubstrate, but it is usually 0.1 μm or more. If the thickness is lessthan 0.1 μm, the concentration of the light absorbing agent required forsufficient light absorption becomes high and this deteriorates thefilm-forming property, and as a result, adhesion to the adjacent layermay fail. On the other hand, if the thickness of the photothermalconversion layer is 5 μm or more while keeping constant theconcentration of the light absorbing agent required to permit theseparation by the thermal decomposition of the photothermal conversionlayer, the light transmittance of the photothermal conversion layer (ora precursor thereof) becomes low. As a result, when a photo-curable, forexample, an ultraviolet (UV)-curable photothermal conversion layer, anda joining layer are used, the curing process is sometimes inhibited tothe extent that a sufficiently cured product cannot be obtained.Therefore, in the case where the photothermal conversion layer is, forexample, ultraviolet-curable, in order to minimize the force required toseparate the substrate from the support after irradiation and to preventthe abrasion of the photothermal conversion layer during grinding, thethickness of the photothermal conversion layer is preferably from about0.3 to about 3 μm, more preferably from about 0.5 to about 2.0 μm.

Joining Layer

The joining layer is used for fixing the substrate to be ground to thesupport through a photothermal conversion layer. After the separation ofthe substrate and the support by the decomposition of the photothermalconversion layer, a substrate having the joining layer thereon isobtained. Therefore, the joining layer must be easily separated from thesubstrate, such as by peeling. Thus, the joining layer has an adhesivestrength high enough to fix the substrate to the support yet low enoughto permit separation from the substrate. Examples of the adhesive whichcan be used as the joining layer in the present invention includerubber-base adhesives obtained by dissolving rubber, elastomer or thelike in a solvent, one-part thermosetting adhesives based on epoxy,urethane or the like, two-part thermosetting adhesives based on epoxy,urethane, acryl or the like, hot-melt adhesives, ultraviolet (UV)- orelectron beam-curable adhesives based on acryl, epoxy or the like, andwater dispersion-type adhesives. UV-curable adhesives obtained by addinga photo-polymerization initiator and, if desired, additives to (1) anoligomer having a polymerizable vinyl group, such as urethane acrylate,epoxy acrylate or polyester acrylate, and/or (2) an acrylic ormethacrylic monomer are suitably used. Examples of additives include athickening agent, a plasticizer, a dispersant, a filler, a fireretardant and a heat stabilizing agent.

In particular, the substrate to be ground such as silicon wafergenerally has asperities such as circuit patterns on one side. For thejoining layer to fill in the asperities of the substrate to be groundand rendering the thickness of the joining layer uniform, the adhesiveused for the joining layer is preferably in a liquid state duringcoating and laminating and preferably has a viscosity of less than10,000 centipoise (cps) at the temperature (for example, 25° C.) of thecoating and laminating operations. This liquid adhesive is preferablycoated by a spin coating method among various methods described later.As such an adhesive, a UV-curable adhesive and a visible light-curableadhesive are particularly preferred, because the thickness of thejoining layer can be made uniform and moreover, the processing speed ishigh for the above-mentioned reason.

The storage modulus of the adhesive is preferably 100 MPa or more at 25°C. and 10 MPa or more at 50° C. under the use conditions after removalof the solvent of the adhesive in the case of a solvent-type adhesive,after curing in the case of a curable adhesive, or after normaltemperature solidification in the case of a hot-melt adhesive. With thiselastic modulus, the substrate to be ground can be prevented fromwarping or distorting due to stress imposed during grinding and can beuniformly ground to an ultrathin substrate. The storage modulus orelastic modulus as used herein can, for example, be measured on anadhesive sample size of 22.7 mm×10 mm×50 μm in a tensile mode at afrequency of 1 Hz, a strain of 0.04% and a temperature ramp rate of 5°C./min. This storage modulus can be measured using SOLIDS ANALYZER RSAII (trade name) manufactured by Rheometrics, Inc.

As the joining layer, a double-faced adhesive tape shown in FIGS. 1( b)to (e) can also be used. In such a double-faced adhesive tape, apressure-sensitive adhesive layer is usually provided on both surfacesof a backing material. Examples of useful pressure-sensitive adhesivesinclude those mainly comprising acryl, urethane, natural rubber or thelike, and those additionally containing a crosslinking agent. Amongthese, preferred is an adhesive comprising 2-ethylhexylacrylate or butylacrylate as the main component. For the backing material, paper or afilm of plastic or the like is used. Here, the backing must havesufficiently high flexibility so as to permit the separation of thejoining layer from the substrate by peeling.

It is also found that in the case of grinding a substrate to anultrathin thickness, a specific photocurable adhesive is preferablyused. Grinding of a substrate to an ultrathin thickness of 50 μm or lesssometimes causes problems such as intrusion of water into the interfacebetween the substrate and the joining layer, edge chipping of thesubstrate or damage in the center portion of the substrate. To avoidthese problems, the grinding is generally performed at a slower rate.This results in grinding times which are as much as twice as long asthose employed for an ordinary finished thickness of 150 μm or more.This is done, for example, by reducing the rotation number of thegrinding wheel so as to prevent damage. In general, an ultrathinsemiconductor wafer is subjected to a polishing step of removing adamage layer (a layer which is damaged by the grinding and not a singlecrystal) remaining after the back surface grinding. In the grinding orpolishing step, to avoid problems such as intrusion of water into theinterface between the substrate and the joining layer, edge chipping ofthe substrate, or damage in the center portion of the substrate withoutsacrificing the grinding speed, the adhesive strength (cleavage mode,see FIG. 9 and the description below) of the joining layer to thesubstrate to be ground at least about 2.0 (N/3.5 cm²) or more whenmeasured as described later on in the Examples.

When the photocurable adhesive is cured on the substrate to be ground,the adhesion area is reduced due to curing shrinkage and the adhesivestrength to the substrate is liable to decrease. In order to ensure theabove-described adhesive strength, the photocurable adhesive ispreferably an adhesive which can recover the adhesive strength underheating to a temperature higher than the glass transition temperature(Tg). Such an adhesive has a minimum storage modulus of 3.0×10⁷ to7.0×10⁷ Pa as measured at a temperature of 25 to 180° C. If the minimumstorage modulus is too high, a sufficiently large adhesive strengthcannot be obtained and this may give rise to intrusion of water into theinterface between the substrate and the joining layer, edge chipping ofthe substrate or damage in the center portion of the substrate. On theother hand, if the minimum storage modulus is excessively low,separation of the joining layer (adhesive layer) may be difficult aftera heating step, such as lamination to a die bonding tape.

Furthermore, the storage modulus at a maximum achievable temperature atthe interface of the substrate and the joining layer during grinding(usually from 40 to 70° C., for example 50° C.) is preferably 9.0×10⁷ Paor more, more preferably 3.0×10⁸ Pa or more. With the storage modulus inthis range, the pressing in the vertical direction by a grinding toolduring the grinding is prevented from causing local deformation of thejoining layer to an extent of damaging the substrate to be ground(silicon wafer).

As an example of a photocurable adhesive that satisfies all of theseconditions, an adhesive where the total amount of bifunctional urethane(meth)acrylate oligomers having a molecular weight of 3,000 or more is40 wt % or more and the total amount of bifunctional (meth)acrylmonomers is 25 wt % or more is known and is suitably used. However, theadhesive is not particularly limited as long as it exhibits necessaryproperties (adhesive strength, functional property).

The thickness of the joining layer is not particularly limited as longas it can ensure the thickness uniformity required for the grinding ofthe substrate to be ground and the tear strength necessary for thepeeling of the joining layer from the wafer after removing the supportfrom the laminated body, and can sufficiently absorb the asperities onthe substrate surface. The thickness of the joining layer is typicallyfrom about 10 to about 150 μm, preferably from about 25 to about 100 μm.

Other Useful Additives

Since the substrate to be ground of the laminated body of the presentinvention can be a wafer having formed thereon a circuit, the wafercircuit may be damaged by radiation energy such as a laser beam reachingthe wafer through the light transmitting support, the photothermalconversion layer and the joining layer. To avoid such circuit damage, alight absorbing dye capable of absorbing light at the wavelength of theradiation energy or a light reflecting pigment capable of reflecting thelight may be contained in any of the layers constituting the laminatedbody or may be contained in a layer separately provided between thephotothermal conversion layer and the wafer. Examples of light absorbingdyes include dyes having an absorption peak in the vicinity of thewavelength of the laser beam used (for example, phthalocyanine-baseddyes and cyanine-based dyes). Examples of light reflecting pigmentsinclude inorganic white pigments such as titanium oxide.

Additional Useful Layers

The laminated body of the present invention may comprise additionallayers other than the substrate to be ground, the joining layer incontact with the substrate to be ground, the photothermal conversionlayer and the light transmitting support. Examples of the additionallayer include a first intermediate layer 6 provided, as shown in FIG. 1(f), between the joining layer 3 and the photothermal conversion layer 4,and/or a second intermediate layer 9 provided between the photothermalconversion layer 4 and the support 5. The second intermediate layer 9 ispreferably joined to the support 5 through a joining layer 3′ (forexample, a pressure-sensitive adhesive).

In the case where the first intermediate layer 6 is provided, thelaminated body 1 is separated at the photothermal conversion layer 4after the irradiation and a laminated body of first intermediate layer6/joining layer 3/substrate 2 is obtained. Therefore, the firstintermediate layer 6 acts as a backing during the separation of thejoining layer 3 from substrate 2 and enables the easy separation of thetwo. The first intermediate layer 6 is preferably a multilayer opticalfilm. Also, the first intermediate layer 6 is preferably a film whichselectively reflects the radiation energy used to enable the separation,such as YAG laser (near infrared wavelength light). This film ispreferred because when the first intermediate layer 6 does not transmitbut reflects radiation energy, the radiation energy is prevented fromreaching the wafer surface, where circuitry is present, and thiseliminates the possibility of damage to the circuitry. In the case ofusing a photocurable adhesive as the joining layer 3, a film having asufficiently high transmittance for curing light such as ultravioletlight is preferred. Accordingly, the multilayer optical film ispreferably transmissive to ultraviolet light and selectively reflectsnear infrared light. The preferred multilayer optical film which istransmissive to ultraviolet light and reflects near infrared light isavailable as 3M™ Solar Reflecting Film (3M Company, St. Paul, Minn.).The first intermediate layer 6 functions as a substrate for the removalof joining layer 3 from substrate 2 by peeling and therefore, preferablyhas a thickness of 20 μm or more, more preferably 30 μm or more, and abreaking strength of 20 MPa or more, more preferably 30 MPa or more,still more preferably 50 MPa or more.

In the case where the above-described second intermediate layer 9 isprovided, a laminated body of second intermediate layer 9/joining layer3′/light transmitting support 5 is obtained after the irradiation of thelaminated body 1. Therefore, the second intermediate layer 9 acts as abacking during the separation of the joining layer 3′ and support 5 andenables the easy separation of the two. As such, by providing a secondintermediate layer, the photothermal conversion layer 4 or the joininglayer 3′ (pressure-sensitive adhesive) is prevented from remaining onthe light transmitting support 5, and the support 5 can be easilyrecycled. In order to enable the removal of joining layer 3′ fromsupport 5 by peeling them apart after the laser irradiation and withoutrupturing, the second intermediate layer 9 preferably has a thickness of20 μm or more, more preferably 30 μm or more, and a breaking strength of20 MPa or more, more preferably 30 MPa or more, still more preferably 50MPa or more. In some cases, the resin of the second intermediate layer 9permeates into the photothermal conversion layer 4, such as when thesecond intermediate layer is coated as a mixture of photocurableoligomer and monomer and cured with UV (e.g., when the sheet is producedby coating photothermal conversion layer on the film substrate, coatingthe second intermediate layer on photothermal conversion layer andcuring it, and coating the joining layer on the second intermediatelayer). In such cases, in order to prevent re-adhering of the surfaceseparated with a space formed by the laser irradiation, the Tg of theresin (in the case of a photocurable resin, the Tg of the cured resin)must be 40° C. or more.

Manufacturing the Laminated Body

In the manufacture of the laminated body, it is important to preventundesirable foreign substances such as air from entering between layers.For example, if air enters between layers, the thickness uniformity ofthe laminated body is prevented and the substrate to be ground cannot beground to a thin substrate. In the case of manufacturing a laminatedbody shown in FIG. 1( a), the following method, for example, may beconsidered. First, the precursor coating solution of the photothermalconversion layer is coated on the support by any one of the methodsdescribed above, dried and cured by irradiating with ultraviolet lightor the like. Thereafter, the joining layer is coated on either one orboth of the surface of the cured photothermal conversion layer and thesurface of the substrate in the non-ground side. The photothermalconversion layer and the substrate are attached through the joininglayer and then, the joining layer is cured, for example, by irradiatingwith ultraviolet light from the support side, whereby a laminated bodycan be formed. The formation of such a laminated body is preferablyperformed under vacuum to prevent air from entering between layers. Thiscan be attained by, for example, by modifying a vacuum adhesion devicesuch as that described in Japanese Unexamined Patent Publication (Kokai)No. 11-283279. In the case of manufacturing a laminated body as shown inFIGS. 1( b) to (e), the laminated body can be easily formed bylaminating the substrate to be ground and the support using adouble-faced tape previously formed in a usual manner. This is alsopreferably performed under vacuum similarly to the above-described case.The laminated body as shown in FIG. 1( f), where the joining layers 3and 3′ are pressure-sensitive adhesive layers, can be produced in thesame manner as the laminated body of FIGS. 1( b) to (e) by forming adouble-coated adhesive tape having a pressure-sensitive adhesive on bothsurfaces of first intermediate layer/photothermal conversionlayer/second intermediate layer, and laminating a substrate to be groundand a support thereto. In this case the second intermediate layer iscoated on the photothermal conversion layer directly and held with thejoining layers 3′ (a pressure-sensitive adhesive or a photocurableadhesive) to the support. In the case where the joining layers 3 and 3′are a photocurable adhesive, the laminated body can be produced in thesame manner as the laminated body shown in FIG. 1( a). The vacuumadhesion device which can be used for forming a laminated body isdescribed below.

The laminated body is preferably designed such that it is free from theinvasion of water used during grinding of the substrate, has an adhesivestrength between layers so as not to cause dropping off of thesubstrate, and has an abrasion resistance so as to prevent thephotothermal conversion layer from being abraded by the water flow(slurry) containing dusts of the ground substrate.

Manufacturing the Thinned Substrate

A thinned substrate can be manufactured by the method comprisingpreparing a laminated body formed as above, grinding the substrate, to adesired thickness, applying radiation energy to the photothermalconversion layer through the light transmitting support to decompose thephotothermal conversion layer and thereby to separate the groundsubstrate from the light transmitting support, and peeling the joininglayer from the substrate.

In one aspect, the method of the present invention is described below byreferring to the drawings. In the following, a laser beam is used as theradiation energy source and a silicon wafer is used as the substrate tobe ground, however, the present invention is not limited thereto.

FIG. 2 shows a cross-sectional view of a vacuum adhesion device suitablefor the production of the laminated body of one embodiment of thepresent invention. A vacuum adhesion device 20 comprises a vacuumchamber 21; a supporting part 22 provided in the vacuum chamber 21, onwhich either one of a substrate 2 to be ground (silicon wafer) or asupport 5 is disposed; and holding/releasing means 23 provided in thevacuum chamber 21 and movable in the vertical direction at the upperportion of the supporting part 22, which holds the other one of thesupport 5 or the silicon wafer 2. The vacuum chamber 21 is connected toa pressure reducing device 25 via pipe 24, so that the pressure insidethe vacuum chamber 21 can be reduced. The holding/releasing means 23 hasa shaft 26 movable up and down in the vertical direction, a contactsurface part 27 provided at the distal end of the shaft 26, leaf springs28 provided in the periphery of the contact surface part 27, and holdingclaws 29 extending from each leaf spring 28. As shown in FIG. 2( a),when the leaf springs are in contact with the upper surface of thevacuum chamber 21, the leaf springs are compressed and the holding claws29 are directed toward the vertical direction to hold the support 5 orthe wafer 2 at peripheral edges. On the other hand, as shown in FIG. 2(b), when the shaft 26 is pressed down and the support 5 or the wafer 2is in close proximity to the wafer 2 or the support 5 respectivelydisposed on the supporting part, the holding claws 29 are releasedtogether with the leaf springs 28 to superimpose the support 5 and thewafer 2.

Using this vacuum adhesion device 20, the laminated body can bemanufactured as follows. First, as described above, a photothermalconversion layer is provided on a support 5. Separately, a wafer to belaminated is prepared. On either one or both of the wafer 2 and thephotothermal conversion layer of the support 5, an adhesive for forminga joining layer is applied. The thus-prepared support 5 and wafer 2 aredisposed in the vacuum chamber 21 of the vacuum adhesion device 20 asshown in FIG. 2( a), the pressure is reduced by the pressure reducingdevice, the shaft 26 is pressed down to laminate the wafer as shown inFIG. 2( b) and after opening to air, the adhesive is cured, if desired,to obtain a laminated body.

FIG. 3 shows a partial cross-sectional view of a grinding device usefulin an embodiment of the invention. The grinding device 30 comprises apedestal 31 and a grinding wheel 33 rotatably mounted on the bottom endof a spindle 32. A suction port 34 is provided beneath the pedestal 31and the suction port 34 is connected to a pressure reducing device (notshown), whereby a material to be ground is suctioned and fixed on thepedestal 31 of the grinding device 30. The laminated body 1 of thepresent invention as shown in FIG. 1 is prepared and used as a materialto be ground. The support side of the laminated body 1 is mounted on thepedestal 31 of the grinding device 30 and fixed by suction using apressure reducing device. Thereafter, while feeding a fluid flow (suchas water or any solution known useful in wafer grinding), the grindingwheel 33 under rotation is brought into contact with the laminated body1, thereby performing the grinding. The grinding can be performed to anultrathin level of 150 μm or less, preferably 50 μm or less, morepreferably 25 μm or less.

After grinding to the desired level, the laminated body 1 is removed andconveyed to subsequent steps, where the separation of the wafer and thesupport by irradiation with a laser beam and the peeling of the joininglayer from the wafer are performed. FIG. 4 shows a drawing of the stepsof separating the support and peeling of the joining layer. First, bytaking account of the final step of dicing, a die bonding tape 41 isdisposed, if desired, on the ground surface of the wafer side of thelaminated body 1 (FIG. 4( a)) or the die bonding tape 41 is not disposed(FIG. 4( a′)), and thereafter, a dicing tape 42 and a dicing frame 43are disposed (FIG. 4( b)). Subsequently, a laser beam 44 is irradiatedfrom the support side of the laminated body 1 (FIG. 4( c)). After theirradiation of the laser beam, the support 5 is picked up to separatethe support 5 from the wafer 2 (FIG. 4( d)). Finally, the joining layer3 is separated by peeling to obtain a thinned silicon wafer 2 (FIG. 4(e)).

Usually, a semiconductor wafer such as silicon wafer is subjected tochamfering called beveling so as to prevent edges from damage due toimpact. That is, the corners at edge parts of a silicon wafer arerounded. When a liquid adhesive is used as the joining layer and coatedby spin coating, the joining layer is spread to the edge parts and theadhesive is exposed to edge parts of the grinding surface. As a result,in disposing a dicing tape, not only the ground wafer but also theexposed adhesive come into contact with the pressure-sensitive adhesiveof the dicing tape. When the adhesion of the dicing tape used is strong,the joining layer is sometimes difficult to separate. In such a case, itis preferred to previously remove a part of the exposed adhesive beforedisposing a dicing tape and a dicing frame. For the removal of theexposed adhesive at edge parts, using radiation energy or a CO₂ laser(wavelength of 10.6 μm) which the adhesive can sufficiently absorb iseffective.

FIG. 5 shows a cross-sectional view of a laminated body fixing devicewhich can be used, for example, in the step of irradiating, such as witha laser beam in one aspect of the invention. The laminated body 1 ismounted on a fixing plate 51 such that the support comes as the uppersurface with respect to the fixing device 50. The fixing plate 51 ismade of a porous metal such as sintered metal or a metal having surfaceroughness. The pressure is reduced from the lower part of the fixingplate 51 by a vacuum device (not shown), whereby the laminated body 1 isfixed by suction onto the fixing plate 51. The vacuum suction force ispreferably strong enough not to cause dropping in the subsequent stepsof separating the support and peeling of the joining layer. A laser beamis used to irradiate the laminated body fixed in this manner. Foremitting the laser beam, a laser beam source having an output highenough to cause decomposition of the heat decomposable resin in thephotothermal conversion layer at the wavelength of light absorbed by thephotothermal conversion layer is selected, so that a decomposition gascan be generated and the support and the wafer can be separated. Forexample, a YAG laser (wavelength of 1,064 nm), a second harmonic YAGlaser (wavelength: 532 nm) and a semiconductor laser (wavelength: from780 to 1,300 nm) can be used.

As the laser irradiation device, a device capable of scanning a laserbeam to form a desired pattern on the irradiated surface and capable ofsetting the laser output and the beam moving speed is selected. Also, inorder to stabilize the processing quality of the irradiated material(laminated body), a device having a large focus depth is selected. Thefocus depth varies depending on the dimensional precision in the designof device and is not particularly limited but the focus depth ispreferably 30 μm or more. FIG. 6 shows a perspective view of a laserirradiation device which can be used in the present invention. The laserirradiation device 60 of FIG. 6( a) is equipped with a galvanometerhaving a biaxial configuration composed of the X axis and the Y axis andis designed such that a laser beam oscillated from a laser oscillator 61is reflected by the Y axis galvanometer 62, further reflected by the Xaxis galvanometer 63 and irradiated on the laminated body 1 on thefixing plate. The irradiation position is determined by the directionsof the galvanometers 62 and 63. The laser irradiation device 60 of FIG.6( b) is equipped with a uniaxial galvanometer or a polygon mirror 64and a stage 66 movable in the direction orthogonal to the scanningdirection. A laser beam from the laser oscillator 61 is reflected by thegalvanometer or polygon 64, further reflected by a hold mirror 65 andirradiated on the laminated body 1 on the movable stage 66. Theirradiation position is determined by the direction of the galvanometeror polygon 64 and the position of the movable stage 66. In the device ofFIG. 6( c), a laser oscillator 61 is mounted on a movable stage 66 whichmoves in the biaxial direction of X and Y, and a laser is irradiated onthe entire surface of the laminated body 1. The device of FIG. 6( d)comprises a fixed laser oscillator 61 and a movable stage 66 which movesin the biaxial direction of X and Y. The device of FIG. 6( e) has aconstitution such that a laser oscillator 61 is mounted on a movablestage 66′ which can move in the uniaxial direction and a laminated body1 is mounted on a movable stage 66″ which can move in the directionorthogonal to the movable stage 66′.

When there is concern about damaging the wafer of the laminated body 1by the laser irradiation, a top hat form (see FIG. 6( f)) having a steepenergy distribution and very reduced leakage energy to the adjacentregion is preferably formed. The beam form may be changed by any knownmethod, for example, by (a) a method of deflecting the beam by anacousto-optic device, a method of forming a beam usingrefraction/diffraction, or (b) a method of cutting the broadeningportion at both edges by using an aperture or a slit.

The laser irradiation energy is determined by the laser power, the beamscanning speed and the beam diameter. For example, the laser power thatcan be used is, but not limited to, from 0.3 to 100 watts (W), thescanning speed is from 0.1 to 40 meters/second (m/s), and the beamdiameter is from 5 to 300 μm or more. In order to increase the speed ofthis step, the laser power is enhanced and thereby the scanning speed isincreased. Since the number of scans can be further reduced as the beamdiameter becomes larger, the beam diameter may be increased when thelaser power is sufficiently high.

The heat decomposable resin in the photothermal conversion layer isdecomposed by the laser irradiation to generate a gas which createscracks inside the layer to separate the photothermal conversion layeritself. If air enters in between the cracks, re-adhesion of the crackscan be prevented. Therefore, in order to facilitate the entering of air,it is desirable to perform the beam scanning from the edge part of thelaminated body to the interior of the laminated body.

As described above, the glass transition temperature (Tg) of thephotothermal conversion layer is preferably room temperature (20° C.) ormore. This is because the separated cracks may re-adhere to one anotherduring the cooling of the decomposed resin and make the separationimpossible. The re-adhesion is considered to occur due to the fact thatthe cracks of the photothermal conversion layer become attached witheach other under the weight of the support. Therefore, the re-adhesioncan be prevented when the irradiation process is contrived not to imposethe weight of the support, for example, by performing the laserirradiation in the vertical direction from the lower part to the upperpart (namely, by performing the laser irradiation in a configurationsuch that the support comes to the bottom side) or by inserting a hookbetween the wafer and the photothermal conversion layer from the edgepart and lifting the layer.

To employ a laser beam from the edge part of the laminated body, amethod of applying the laser beam while linearly reciprocating it fromthe edge part to the tangential direction of wafer or, alternatively, amethod of spirally irradiating the laser beam from the edge part to thecenter like a phonograph record may be used.

After the laser irradiation, the support is separated from the wafer andfor this operation, a general pick-up using a vacuum is used. Thepick-up is a cylindrical member connected to a vacuum device having asuction device at the distal end. FIG. 7 shows a schematic view of apick-up for use in the separation operation of the wafer and thesupport. In the case of FIG. 7( a), the pick-up 70 is in the center ofthe support 5 and picked up in the vertical direction, thereby peelingoff the support. Also, as shown in FIG. 7( b), the pick-up 70 is at theedge part of the support 5 and by peeling while blowing a compressed air(A) from the side to enter air between the wafer 2 and the support 5,the support can be more easily peeled off.

After removing the support, the joining layer on the wafer is removed.FIG. 8 is a schematic view showing how the joining layer is peeled. Forthe removal of the joining layer 3, preferably, an adhesive tape 80 forremoving the joining layer, which can create a stronger adhesive bondwith joining layer 3 than the adhesive bond between the wafer 2 and thejoining layer 3, can be used. Such an adhesive tape 80 is placed toadhere onto the joining layer 3 and then peeled in the arrow direction,whereby the joining layer 3 is removed.

Finally, a thinned wafer remains in the state of being fixed to a dicingtape or a die frame with or without a die bonding tape. This wafer isdiced in a usual manner, thereby completing a chip. However, the dicingmay be performed before the laser irradiation. In such a case, it isalso possible to perform the dicing step while leaving the waferattached to the support, then subject only the diced region to the laserirradiation and separate the support only in the diced portion. Thepresent invention may also be applied separately to a dicing stepwithout using a dicing tape, by re-transferring through a joining layerthe ground wafer onto a light transmitting support having providedthereon a photothermal conversion layer.

The present invention is effective, for example, in the followingapplications.

1. Laminated CSP (Chip Size Package) for High-Density Packaging

The present invention is useful, for example, with a device form calledsystem-in-package where a plurality of Large Scale Integrated (LSI)devices and passive parts are housed in a single package to realizemultifunction or high performance, and is called a stacked multi-chippackage. According to the present invention, a wafer of 25 μm or lesscan be reliably manufactured in a high yield for these devices.

2. Through-Type CSP Requiring High Function and High-Speed Processing

In this device, the chips are connected by a through electrode, wherebythe wiring length is shortened and the electrical properties areimproved. To solve technical problems, such as formation of a throughhole for forming a through electrode and embedding of copper in thethrough hole, the chip must be further reduced in the thickness. In thecase of sequentially forming chips having such a configuration by usingthe laminated body of the present invention, an insulating film and abump (electrode) must be formed on the back surface of the wafer and thelaminated body needs resistance against heat and chemicals. Even in thiscase, when the above-described support, photothermal conversion layerand joining layer are selected, the present invention can be effectivelyapplied.

3. Ultrathin Compound Semiconductor (e.g. GaAs) Improved in HeatRadiation Efficiency, Electrical Properties and Stability

Compound semiconductors such as gallium arsenide are being used forhigh-performance discrete chips, laser diode and the like because oftheir advantageous electrical properties (high electron mobility, directtransition-type band structure) over silicon. Using the laminated bodyof the present invention and thereby reducing the thickness of the chipincreases the heat dissipation efficiency thereof and improvesperformance. At present, the grinding operation for thickness reductionand the formation of an electrode are performed by joining asemiconductor wafer to a glass substrate as the support using a greaseor a resist material. Therefore, the joining material must be dissolvedby a solvent for separating the wafer from the glass substrate after thecompletion of processing. This is accompanied with problems that theseparation requires more than several days time and the waste solutionmust be treated. These problems can be solved when the laminated body ofthe present invention is used.

4. Application to Large Wafer for Improving Productivity

In the case of a large wafer (for example, a 12 inch-diameter siliconwafer), it is very important to separate the wafer and the supporteasily. The separation can be easily performed when the laminated bodyof the present invention is used, and therefore, the present inventioncan be applied also to this field.

5. Ultrathin Rock Crystal Wafer

In the field of rock crystal wafer, the thickness reduction of a waferis required to increase the oscillation frequency. The separation can beeasily performed when the laminated body of the present invention isused, and therefore, the present invention can be applied also to thisfield.

EXAMPLES

The present invention is described in greater detail below by referringto Examples.

First, by using various conditions of laser irradiation, thecharacteristics preferred for separation of the support and the waferwas evaluated. Since the property for separation depends on the degreeof decomposition of the photothermal conversion layer by laserirradiation, a glass substrate was used in place of the ground wafer. Asthe light transmitting support, a glass substrate of 127 millimeters(mm)×94 mm×0.7 mm was used, and in place of the wafer, the same glasssubstrate as above was used. A 10% solution (in propylene glycolmethylether acetate solvent) of a photothermal conversion layerprecursor having the composition shown in Table 1 below was coated onthe glass substrate by spin coating.

TABLE 1 Photothermal Conversion Layer Solid Content Ratio EC600JD 15.91%Solasperse 5000 0.80% Disperbyk 161 12.78% UR8300 39.81% Ebecryl EB62911.64% TMPTA-N 11.64% Irgacure 369 6.47% Irgacure 184 0.96% Total100.00%

EC600JD (Ketjen Black International Co.): carbon black, average particlesize 30 nm; Solsperse 5000 (Zeneca Co., Ltd.): dispersion aid; Disperbyk161 (BYK Chemie Japan Co., Ltd.): dispersant (30% in butyl acetate);UR8300 (Toyobo Co., Ltd.): urethane modified polyester resin (30% intoluene/methyl ethyl ketone), MW=30000, Tg=23° C., strength at breakage400 kg/cm2, elongation at break 500%; Ebecryl EB629 (Daicel UCB Co.Ltd.): novolak epoxy acrylate diluted 33% with a monomer (TMPTA),oligomer MW=550.

TMPTA-N (Daicel UCB Co. Ltd.): trimethylolpropane triacrylate; Irgacure369 (Ciba Specialty Chemicals K.K.):2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone; andIrgacure 184 (Ciba Specialty Chemicals K.K.): 1-hydroxycyclohexyl phenylketone.

This was dried by heating (80° C., 2 min) and then cured by ultraviolet(UV) irradiation to form a photothermal conversion layer on the support.A joining layer precursor having the composition shown in Table 2 belowwas coated dropwise on another glass substrate. These substrates werelaminated to each other and UV was irradiated thereon to cure thejoining layer precursor, thereby obtaining a laminated body.

TABLE 2 Joining layer Solid Content Ratio UV-6100B 57.10% HDODA 38.10%Darocure1173 4.80% Total 100.00%

UV-6100B (Nippon Synthetic Chemical Industry Co., Ltd): acrylatedurethane oligomer, MW=6700, Tg 0° C. after UV cure; HDODA (Daicel UCB):1,6-hexanediol diacrylate; Darocurel 173 (Ciba Specialty Chems.):2-hydroxy-2-methyl-1-phenylpropan-1-one.

This laminated body had a configuration of glass substrate/photothermalconversion layer/joining layer/glass substrate, the thickness of thephotothermal conversion layer was 0.9 μm and the thickness of thejoining layer was 100 μm. This laminated body was disposed on a fixingplate of a laminated body fixing device as shown in FIG. 4 and thepressure was reduced from the lower side by a vacuum device to fix thelaminated body by suction on the fixing plate. As a laser beam sourcefor the radiation energy, a YAG laser (wavelength: 1,064 nm) was used.The laser output was varied in the range from 0.52 to 8.00 W, the beamdiameter and the scanning pitch were the same and were varied in therange from 90 to 200 μm, the laser scanning speed was varied in therange from 0.2 to 5 m/s, the laser beam was applied by linearlyreciprocating it from the edge part of the laminated body, and the laserbeam was irradiated over the entire surface of the laminated body.

A pressure-sensitive adhesive tape (SCOTCH™ pressure-sensitive adhesivetape available as #3305 from 3M Company, St. Paul, Minn.) was attachedto the glass substrate of the laminated body thus irradiated with alaser beam, and then picked up.

By this preliminary test, it was found that the glass substrates can beseparated in good condition when the laser output is 6.0 to 8.0 W, thebeam diameter and the scanning pitch is 100 to 200 μm, and the laserscanning speed is 0.2 to 2.0 m/s.

Example 1

A glass substrate of 220 mm (diameter)×1.0 mm (thickness) was used asthe light permeable support, and a silicon wafer of 200 mm(diameter)×750 μm (thickness) was used as the wafer. A 10% solution (inpropylene glycol methylether acetate solvent) of a photothermalconversion layer precursor having the composition shown in Table 1 abovewas coated on the glass substrate by spin coating. This was dried byheating and then cured by ultraviolet (UV) irradiation to form aphotothermal conversion layer on the support. A joining layer precursorhaving the composition shown in Table 2 above was coated on the wafersimilarly by spin coating. The glass substrate and the wafer werelaminated to each other in a vacuum adhesion device as shown in FIG. 2and thereon, was irradiated with UV light to cure the joining layerprecursor, thereby obtaining a laminated body. This laminated body had aconfiguration of glass substrate/photothermal conversion layer/joininglayer/silicon wafer, the thickness of the photothermal conversion layerwas 0.9 μm, the thickness of the joining layer was 100 μm, and theadhesion area was 314 cm².

The laminated body obtained was disposed on a grinding device as shownin FIG. 3 and while feeding a water flow the grinding wheel underrotation was brought into contact with the laminated body, therebyperforming the grinding. The grinding was performed to provide a waferthickness of 50 μm. A dicing tape and a dicing frame were then disposedon the ground surface of the wafer and the laminated body was conveyedonto the fixing plate of a laminated body fixing device as shown in FIG.5, where the pressure was reduced from the lower side by a vacuum deviceto thereby fix the laminated body by suction on the fixing plate.

Based on the results in the preliminary test above, the laserirradiation was performed using a YAG laser (wavelength: 1,064 nm) wherethe laser output was 6.0 W, the beam diameter and the scanning pitcheach was 100 μm, and the laser scanning speed was 1.0 m/s. The laserbeam irradiated the laminated body by linearly reciprocating from theedge part of the laminated body to the tangential direction. In thismanner the entire surface of the laminated body irradiated. A suctiondevice was fixed to the glass plate of the irradiated laminated bodywhich was then was picked up, whereby the glass plate was easilyseparated from the wafer and a wafer having a joining layer thereon wasobtained.

For peeling the joining layer from the wafer, a pressure-sensitiveadhesive tape (SCOTCH™ #3305 Wafer De-taping Tape from 3M) was attachedto the surface of the joining layer and peeled back in the direction of180°, whereby a silicon wafer having a thickness of 50 μm was obtainedwithout damaging the wafer.

Example 2

In this Example, the test was performed in the same manner as in Example1 except for the following modifications. As the photothermal conversionlayer precursor, a 20% solution (in propylene glycol methyletheracetate) having the composition at a solid content ratio shown in Table3 below was used. Furthermore, in order to prevent re-adhesion due tothe weight of the glass substrate during laser irradiation, an L-shapedhook was inserted into the edge part of the glass substrate and hung upwith a spring, whereby re-adhesion due to the weight of the glasssubstrate during laser beam irradiation was prevented. Similarly toExample 1, a silicon wafer having a thickness of 50 μm could be obtainedwithout damaging the wafer.

TABLE 3 Photothermal Conversion Layer Solid Content Ratio Raven 76027.64% Disperbyk 161 13.82% Ebecryl 8804 50.49% Irgacure 369 7.00%Irgacure 184 1.05% Total 100.00%

Raven 760 (Columbian Carbon Japan Ltd.): carbon black; Disperbyk 161(BYK Chemie): dispersant (30% in butyl acetate); Ebecryl 8804 (DaicelUCB): Aliphatic urethane diacrylate, MW=1400 (30% in toluene); Irgacure369 (Ciba Specialty Chemicals K.K.):2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone; Irgacure184 (also from Ciba): 1-hydroxycyclohexyl phenyl ketone.

Example 3

In this Example, the test was performed in the same manner as in Example2 except that a 10% solution (in propylene glycol methylether acetate)having the composition at a solid content ratio shown in Table 4 belowwas used as the photothermal conversion layer precursor. Thisphotothermal conversion layer precursor is a polymer solution containingcarbon black and therefore, the photothermal conversion layer was formedonly by drying.

TABLE 4 Photothermal Conversion Layer Solid Content Ratio Raven 76030.06% Disperbyk 161 15.03% UR8300 54.91% Total 100.00%

Raven 760 carbon black; Disperbyk 161 dispersant; UR8300 polyurethanepolyester.

A silicon wafer having a thickness of 50 μm could be obtained withoutdamaging the wafer by the same operation similarly to Example 1.

Comparative Example 1

A test was performed in the same manner as in Example 1 except that alaminated body consisting of silicon wafer/pressure-sensitive adhesivetape/glass substrate was prepared using no photothermal conversion layerand using, in place of the joining layer, a double-facedpressure-sensitive adhesive tape (SCOTCH™ #9415 high tack/low tack),with the lower tack adhesive in contact with the wafer. The siliconwafer could not be peeled.

Examples 4 to 10

In the following, tests were performed in the same manner as in Examples1 to 3 by variously changing the composition and thickness of thephotothermal conversion layer and using an adhesive (high elasticmodulus-type adhesive) having the same composition as used in Examples 1to 3 or an adhesive (low elastic modulus-type adhesive) having thefollowing composition. The thickness of the joining layer was 50 μm. Thesilicon wafer was ground to 25 μm. The composition and thickness of thephotothermal conversion layer and the composition of the joining layerin each Example are shown in Tables 5 and 6. In Examples 4 to 6, silicawas incorporated as a transparent filler.

TABLE 5 Weight Volume Photothermal Conversion Layer A (containingsilica) Black Pearls 130 25.0% 18.6% AEROSIL 380 22.0% 13.8% Disperbyk161 7.5% 9.4% Joncryl 690 45.5% 58.3% Total 100.0% 100.0% PhotothermalConversion Layer B (containing silica) Black Pearls 130 25.0% 17.9%AEROSIL 380 16.5% 10.0% Disperbyk 161 7.5% 9.0% Joncryl 690 51.0% 63.1%Total 100.0% 100.0% Photothermal Conversion Layer C (containing silica)Black Pearls 130 25.0% 17.3% AEROSIL 380 11.0% 6.4% Disperbyk 161 7.5%8.7% Joncryl 690 56.5% 67.5% Total 100.0% 100.0% Photothermal ConversionLayer D Black Pearls 130 65.0% 52.4% Disperbyk 161 32.5% 26.5% Joncryl690 2.5% 21.1% Total 100.0% 100.0% Photothermal Conversion Layer E BlackPearls 130 45.0% 32.4% Disperbyk 161 22.5% 16.3% Joncryl 690 32.5% 51.3%Total 100.0% 100.0% Joining Layer A (low elastic modulus) UV 6100B 38.1%HDODA 25.4% HOA-MS 31.7% Irgacure 369 4.8% Total 100.0% Joining Layer B(high elastic modulus) UV 6100B 57.1% HDODA 38.1% Irgacure 369 4.8%Total 100.0%Photothermal Conversion Layer Materials:

Black Pearls 130 (Cabot Corporation) carbon black; EC600JD carbon black;AEROSIL 380 (Nippon Aerosil Co.) silica filler; Joncryl 690 (JohnsonPolymer Co.): polyacrylate resin, acid number=240, MW=15500, Tg=102° C.;Disperbyk 161 (BYK Chemie Japan Co., Ltd): dispersant; Solsperse 5000(Zeneca Co., Ltd): dispersant

Joining Layer Materials:

UV-6100B (The Nippon Synthetic Chemical Industry Co., Ltd): acrylatedurethane oligomer, MW=6700, Tg 0° C. after UV cure; HDODA (Daicel UCBCompany Ltd.): 1,6-hexanediol diacrylate; HOA-MS (Kyoeisha Chemical Co.,Ltd) 2-acryloyloxy ethylsuccinic acid; Irgacure 369 (Ciba SpecialtyChemicals K.K.)2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone.

TABLE 6 Photothermal Conversion Layer Example Composition Thickness (μm)Example 4 A (containing silica) 0.9 Example 5 B (containing silica) 0.9Example 6 C (containing silica) 0.9 Example 7 D 0.9 Example 8 D 0.3Example 9 E 0.9 Example 10 E 0.5

In each Example, two kinds of samples, one using a high elastic modulusadhesive as a joining layer and another using a low elastic modulusadhesive as a joining layer, were prepared.

In the tests, the separation of the wafer and the glass substrate wasperformed through the procedure described in Example 1. The test resultsare shown in Table 7 below.

TABLE 7 Separation Force for Laminated Body from Glass PhotothermalConversion Layer Force at the separating of Glass Amount of filler(N/314 cm²) (light absorbing High Elastic Low Elastic agent/transparentThickness Modulus-Type Modulus-Type Example filler) FVC TFVC*⁴ FVC/TFVC(μm) UV Transmittance*¹ Joining Layer*² Joining Layer*³ 4 carbon/silica32.4% 28.4% 114.1% 0.9 2.05% 2.0  5.6 5 carbon/silica 27.9% 30.0% 92.9%0.9 2.05% 1.6  28.0 6 carbon/silica 23.7% 32.5% 73.1% 0.9 2.05% 2.4>50*⁵ 7 Carbon 52.6% 43.9% 119.7% 0.9 0.04% 3.2  0.4 8 Carbon 52.6%43.9% 119.7% 0.3 2.05% 2.0 >50*⁵ 9 Carbon 32.4% 43.9% 73.8% 0.9 0.46%3.2 >50*⁵ 10 Carbon 32.4% 43.9% 73.8% 0.5 2.05% 6.4 >50*⁵ *¹Measuredvalue at a wavelength of 365 nm. *²Elastic modulus at 25° C. is 320 MPa.*³Elastic modulus at 25° C. is 10 MPa. *⁴FVC (filler volumeconcentration); TFVC (top filler volume concentration) which can bedetermined from the void volume of filler in the dry state using theamount of liquid (oil absorption amount) necessary for filling thefiller voids as described above. *⁵The wafer and the support can beeasily separated by using a re-adhesion preventing mechanism.As seen above, when a high elastic modulus-type joining layer was used,the glass substrate and the 25-μm wafer could be easily separated in allof Examples 4 to 10. When a low elastic modulus-type joining layer wasused, the glass substrate and the wafer could not be easily separated inExamples 6 and 8 to 10 where FVC/TFVC was 80% or less. In Example 8, theFVC/TFVC was 80% or more but since the thickness of the photothermalconversion layer was low (0.3 μm), re-adhesion occurred due to localexposure of the joining layer to the separation surface and a largeforce was necessary. In Examples 6 and 8 to 10, the test samples wereagain produced and tested in the same manner as in Examples 2 and 3 byusing a re-adhesion preventing mechanism (hanging up mechanism using anL-shaped hook and a spring) as described in Examples 2 and 3. In thiscase, the glass substrate and the 25-μm wafer could be easily separated.In Examples 4 and 5 where not only carbon black but also silica wereused, even if FVC/TFVC was 80% or more, an ultraviolet (365 nm)transmittance of about 2% could be ensured and the joining layer using aUV-curable adhesive could be cured within a short time.

Examples 11 to 14 Joining Layer Preferred in Some Embodiments

In these examples, a laminated body of the present invention wasproduced using materials in the compositions for the photothermalconversion layer and the adhesive shown in Tables below.

TABLE 8 Chemical Name Trade Name Weight Percentage Adhesive Layer 1Urethane acrylate UV7000B 28.6% Urethane acrylate UV6100B 28.6%1,6-Hexanediol diacrylate 1,6-HX-A 38.1% Photoreaction initiatorIrgacure 369 4.8% Total 100.0% Adhesive Layer 2 Urethane acrylateUV7000B 47.6% Dicyclopentanyl acrylate FA513A 19.0% 1-6-Hexanedioldiacrylate 1,6-HX-A 28.6% Photoreaction initiator Irgacure 369 4.8%Total 100.0%

TABLE 9 Adhesive Layer 3 Chemical Name Trade Name Weight PercentageUrethane acrylate UV6100B 57.1% 1-6-Hexanediol diacrylate 1,6-HX-A 38.1%Photoreaction initiator Irgacure 369 4.8% Total 100.0%

TABLE 10 Photothermal Conversion Layer Chemical Name Trade Name WeightPercentage Carbon black Sevacarb 25.0% Silica A200 32.5% DispersantDisperbyk 16 7.5% Acryl resin Joncryl 690 35.0% Total 100.0%Adhesive Materials:

UV-6100B (The Nippon Synthetic Chemical Industry Co., Ltd.) Acrylatedurethane oligomer, MW=6700, Tg after UV-cure=0 C and UV-7000B (alsoNippon Synthetic Chem.) Acrylated urethane oligomer, MW=3500, Tg 520after UV-cure; 1.6-HX-A (Kyoeisha Chemical Co., Ltd.); FA513A (HitachiChemical Co., Ltd.); HOA-MS (Kyoeisha Chemical Co., Ltd.); DCPA(Kyoeisha Chemical Co., Ltd.); Irgacure 369 (Ciba Specialty ChemicalsK.K.)

Photothermal Conversion Layer Materials:

Sevacarb (Columbian Carbon Japan Ltd.); Aerosil 200 (Nippon AerosilCo.); Joncryl 690 (Johnson Polymer Co.); Disperbyk 161 (BYK Chemie JapanCo., Ltd.)

Adhesives 1 to 3 were measured for storage modulus using a sample havinga size of 22.7 mm×10 mm×50 μm in a tensile mode at a frequency of 1 Hz,a strain of 0.04% and a temperature ramp rate of 5° C./min using SOLIDSANALYZER RSA II from Rheometrics, Inc. The results are shown in Table11. In the Table, an elastic modulus at 50° C. is shown assuming thatthe maximum temperature encountered during the grinding is 50° C.Furthermore, a minimum elastic modulus measured at 25 to 180° C. is alsoshown.

To confirm the adhesive bond strength as the joining layer, eachadhesive was measured for bond strength (cleavage mode) by the followingmethod. As shown in FIG. 9, a silicon wafer 92 was fixed on a horizontalsupporting table 91 through a strong pressure-sensitive adhesivedouble-coated tape. On the silicon wafer 92, a joining layer(Adhesive 1) was coated to an area of 3.5 cm², dried and photo-cured toobtain a joining layer 93 having a thickness of 50 μm. To the curedjoining layer 93, an L-shaped measuring jig 94 having a contact area of3.5 cm² was bonded through a pressure-sensitive adhesive double-coatedtape. A wire was connected to the vertical end part of the L-shapedmeasuring jig 94, a weight 95 was hung to apply the tensile force in thehorizontal direction and the weight was moved at a tensile speed of 20mm/min. The load at breaking is shown as an adhesive bond strength(cleavage mode) in Table 11. Furthermore, a preliminary heat treatment(140° C., 3 minutes) for recovering the adhesive strength was performed.The adhesive strength after the preliminary heat treatment is showntogether in Table 11.

Example 11

A glass substrate having coated thereon a photothermal conversion layerwas laminated with a silicon wafer through Adhesive 1 having a thicknessof 50 μm and cured with ultraviolet light. The adhesion area was 314cm². The wafer surface of the laminated sample was ground to provide awafer thickness of 25 μm using a grinder while supplying grinding waterand then the damage layer (about 2 μm) was removed by a dry polishingdevice. Simulating thermal press-bonding with a die bonding tape, theobtained sample was held on a hot plate at 180° C. for 3 minutes.Furthermore, laser irradiation was carried out from the glass side toremove the glass substrate and then, the adhesive was removed bypeeling. The grinding conditions were as follows.

-   (1) Grinding device: Model DFG850E manufactured by DISCO-   (2) Grinding conditions:

Coarse Grinding Finish Grinding Wafer thickness 750 to 60 μm 60 to 25 μmGrinding Wheel No. (JIS#)  380 2000 Rotations per minute (rpm) of 48005500 grinding wheel

Example 12

A test was performed by the same procedure as in Example 11 except thatAdhesive 2 was used and after the lamination, the sample before grindingwas held in an oven at 140° C. for 3 minutes as a preliminary heattreatment.

Example 13

A test was performed by the same procedure as in Example 11 except thatAdhesive 3 was used and the adhesive thickness was changed to 25 μm.

Example 14

A test was performed by the same procedure as in Example 11 except thatAdhesive 3 was used and the grinding finish thickness of wafer waschanged to 50 μm.

TABLE 11 Thickness Adhesive of Wafer Minimum Initial Strength afterAdhesive After Elastic Elastic Adhesive Preliminary Trouble SeparationThickness Grinding Modulus at Modulus at 25 Strength Heat Treatmentduring Failure after Example Adhesive (μm) (μm) 50° C. (Pa) to 180° C.(Pa) (N/3.5 cm²) (N/3.5 cm²)* Grinding Heat Treatment 11 1 50 25 3.8E+086.2E+07 2.6 — none none 12 2 50 25 1.1E+09 4.2E+07 1.8 3.0 none none 133 25 25 9.4E+07 4.8E+07 3.1 — none none 14 3 50 50 9.4E+07 4.8E+07 3.1 —none none *Preliminary heat treatment (140° C., 3 minutes)As apparent from Table 11, even when the grinding was performed underthe same conditions as in the ordinary grinding to 150 μm, troubles suchas edge chipping during grinding or intrusion of water into theinterface between the wafer and the joining layer were not broughtabout. A sufficiently high adhesive strength was obtained after thepreliminary heat treatment and this was accompanied without the problemof being unable to separate the joining layer from the wafer due toincrease in the adhesive strength of the joining layer after thepreliminary heat treatment. This reveals that also in the removal (forexample, a chemical etching method with chemicals, a CMP method ofmechanically and chemically performing the polishing using a slurry, ora dry polishing method of performing the polishing without usingchemicals at all) of the damage layer (a layer which is damaged by thegrinding and not a single crystal) remaining on the wafer aftergrinding, a phenomenon of edge chipping or stripping does not occur.

Examples 15 and 16 Laminated Body Containing Additional Layers

In these Examples, a laminated body containing a first intermediatelayer and a second intermediate layer was produced.

The following were used as the photothermal conversion layer, the secondintermediate layer, the pressure-sensitive adhesive, the photocurableadhesive, the light transmitting support (glass substrate) and thesubstrate to be ground.

TABLE 12 Photothermal Conversion Layer Chemical Name Trade Name WeightPercentage Carbon black Sevacarb 25.0% Silica A200 32.5% dispersantDisperbyk 16 7.5% Acryl resin Joncryl 690 35.0% Total 100.0%

TABLE 13 Second Intermediate Layer Chemical Name Trade Name WeightPercentage Urethane acrylate UV7000B 47.6% Dicyclopentanyl acrylateFA513A 47.6% Photoreaction initiator Irgacure 369 4.8% Total 100.0%

TABLE 14 Pressure-Sensitive Adhesive Chemical Name Trade Name WeightPercentage Polyurethane polyester UR8700 25.0% Polyurethane polyesterUR3200 75.0% Total 100.0%Glass Substrate: TENPAX heat-resistance glass

TABLE 15 Photocurable Adhesive Chemical Name Trade Name WeightPercentage Urethane acrylate UV6100B 57.1% 1,6-Hexanediol diacrylate1.6-HX-A 38.1% Photoreaction initiator Irgacure 369 4.8% Total 100.0%Material to be Ground: Silicon wafer with a thickness of 750 μm.Raw (Precursor) Materials:

Sevacarb (Columbian Carbon Japan Ltd.); Aerosil 200 (Nippon AerosilCo.); Disperbyk 161 (BYK Chemie Japan Co., Ltd.); Joncryl 690 (JohnsonPolymer Co.); UV7000B, UV6100B (The Nippon Synthetic Chemical IndustryCo., Ltd.); FA513A (Hitachi Chemical Co., Ltd.); 1.6-HX-A (KyoeishaChemical Co., Ltd.); Irgacure 369 (Ciba Specialty Chemicals K.K.);UR8700:Urethane modified polyester resin, MW=32000, Tg=−22° C. Strengthat break <100 kg/cm², Elongation at break 1000%; UR3200:Urethanemodified polyester resin, MW=40000, Tg=−3° C. Strength at break <100kg/cm², Elongation at break 700% (both from Toyobo Co., Ltd.)

Example 15

a) Preparation of Laminated Body

A photothermal conversion layer (1 μm) was coated and dried on a 50-μmpolyethylene terephthalate (PET) film (TEIJIN O Film, produced by TejinLtd.) (corresponding to the first intermediate layer in FIG. 1( f)) andthereon, an intermediate layer (corresponding to the second intermediatelayer 9 in FIG. 1( f) (30 μm) was coated and dried. Furthermore, apressure-sensitive adhesive (10 μm) was coated thereon to prepare apressure-sensitive adhesive single-coated tape. Subsequently, this tapewas laminated with a glass substrate using a roller to obtain glasssubstrate/pressure-sensitive adhesive layer/second intermediatelayer/photothermal transfer layer/PET film (first intermediate layer).

Separately, a photocurable adhesive was coated on a silicon wafer. Then,this silicon wafer was laminated to the exposed PET film surface of theglass substrate/pressure-sensitive adhesive layer/second intermediatelayer/photothermal conversion layer/PET film (first intermediate layer)article by means of the photocurable adhesive and irradiated with UVlight from the glass substrate side to cure the adhesive. The adhesionarea of the laminate was 314 cm².

b) Back Surface Grinding

The back surface of the silicon wafer in the laminated body state wasground to 50 μm.

c) Separation of Glass Substrate

The ground wafer surface of the resulting laminated body was attached toa dicing tape and then fixed on a vacuum chuck table. Then, a YAG laser(output: 7 W, wavelength: 1,064 nm) was used to irradiate the entiresurface from the glass substrate side and thereby, the glass substratewas separated long with pressure sensitive adhesive/second intermediatelayer from the PET Film (first intermediate layer).

d) Separation of Joining Layer

A pressure-sensitive adhesive tape (SCOTCH™ #3305, from 3M) was attachedto the exposed surface of the first intermediate layer (PET film) andpulled up to remove the film and the joining layer from the wafersubstrate.

e) Separation of Pressure-Sensitive Adhesive and Second IntermediateLayer

A pressure-sensitive adhesive tape (#3305) was attached to the exposedsurface of the second intermediate layer and pulled up to remove en blocthe intermediate layer and the pressure-sensitive adhesive from theglass substrate.

Results:

It was confirmed that the adhesive layer was removed together with thefilm from the wafer surface without causing rupturing of the adhesivelayer. On the wafer surface, residual glue and the like were notobserved.

It was also confirmed that the intermediate layer and thepressure-sensitive adhesive were removed en bloc from the glasssubstrate surface. The glass substrate could be recycled by washing itwith ethyl alcohol and pure water.

Example 16

A laminated body was produced and tested in the same manner as inExample 15 except that a multilayer optical film (3M™ Solar ReflectingFilm, from 3M) was used in place of the PET film.

Results:

It was confirmed that the adhesive layer was removed together with thefilm from the wafer surface without causing rupturing of the adhesivelayer. On the wafer surface, residual glue and the like were notobserved.

It was also confirmed that the intermediate layer and thepressure-sensitive adhesive were removed en bloc from the glasssubstrate surface. The glass substrate could be recycled by washing itwith ethyl alcohol and pure water. Furthermore, since a multilayeroptical film which transmits light necessary for curing the photocurableadhesive to form a joining layer and reflects laser light necessary forthe radiation energy treatment was used, the joining layer could becured without any problem and at the same time, the circuitry pattern onthe wafer could be protected from damage by the laser light.

The laminated body of the present invention enables the separating of asubstrate ground to a very small thickness, from a support withoutdamaging the substrate. The support and the substrate are separated by aradiation energy such as a laser beam, so that the joining layer can beeasily separated from the substrate by peeling and an ultrathinsubstrate can be manufactured without damaging the substrate.

What is claimed is:
 1. An apparatus for manufacturing a ground laminatedbody comprising: a vacuum chamber capable of being reduced to apredetermined pressure; a supporting part provided in said vacuumchamber; a substrate; a light transmitting support having formed thereona photothermal conversion layer, wherein either the substrate or thelight transmitting support are disposed on the supporting part; ajoining layer comprising a liquid adhesive, wherein the joining layer isapplied to one or both of the substrate and the photothermal conversionlayer on the light transmitting support; and holding and releasing meansprovided in said vacuum chamber and movable in the vertical directiontowards an upper portion of said supporting part, wherein the other oneof the substrate or the light transmitting support having formed thereonthe photothermal conversion layer is held at the peripheral edges and isreleased when the substrate and the photothermal conversion layer are inclose proximity thereby forming a laminated body; and a grinder forforming a ground surface on one side of the substrate in the laminatedbody; and a tape disposed on the ground surface of the substrate in thelaminated body.
 2. An apparatus according to claim 1, wherein thesubstrate comprises a semiconductor wafer.
 3. An apparatus according toclaim 1, wherein the photothermal conversion layer comprises a lightabsorbing agent and a heat decomposable resin disposed beneath thejoining layer.
 4. An apparatus according to claim 1, wherein the lighttransmitting support comprises glass.
 5. An apparatus according to claim1, wherein the joining layer comprises a photocurable adhesive.
 6. Anapparatus according to claim 1, wherein the liquid adhesive is selectedfrom the group consisting of rubber-base adhesives; one-partthermosetting adhesives based on epoxy or urethane; two-partthermosetting adhesives based on epoxy, urethane, or acryl; hot-meltadhesives based on acryl or epoxy; ultraviolet-curable adhesives basedon acryl or epoxy; visible light-curable adhesives based on acryl orepoxy; electron beam-curable adhesives based on acryl or epoxy; andwater dispersion-type adhesives.
 7. An apparatus according to claim 1,wherein an intermediate layer is located between said photothermalconversion layer and said light transmitting support, and wherein theintermediate layer and the light transmitting support are joinedtogether through another joining layer.
 8. An apparatus according toclaim 1, wherein the holding and releasing means comprises a shaft thatis moveable up and down in the vertical direction, a contact surfacepart provided at the distal end of the shaft, leaf springs provided onthe periphery of the contact surface part, and holding claws extendingfrom each leaf spring.
 9. An apparatus according to claim 8, wherein theholding and releasing means comprises a shaft that is moveable up anddown in the vertical direction.
 10. An apparatus according to claim 9,wherein a downward force is applied to the shaft.
 11. An apparatusaccording to claim 9, further comprising a laminated body.
 12. Anapparatus according to claim 1, wherein the grinder is a grinding wheel.